This invention relates to a new system for traffic mitigation. More specifically, it relates to a system for the cooperative driving between vehicles whereby the flow of automobiles on freeways and city streets at peak hours is substantially increased.
Heavy rush hour traffic is considered an urgent unsolved problem in all major metropolitan areas of the United States. For example, planners in Santa Clara County, Calif., 50 miles south of San Francisco, have declared traffic congestion to be the region's number one public problem. The final bits and pieces of the freeway systems planned and begun in the 50's and 60's are now being completed. Major new highway construction is dubious since the public mood does not support it. Each mile and each interchange is fought by no-growth proponents. Public transit systems are recognized to have only marginal value in areas of low population density, such as Santa Clara County. Even the staunchest advocates of public transit do not think it can replace the private automobile in low density areas.
With major freeway expansions and the replacement of the car by public transit being unlikely, traffic congestion grows worse every year. As a result, there have been several attempts to make the automobile more efficient in heavy traffic thereby allowing already existing freeways and city streets to handle rush hour traffic more easily.
One such attempt is the idea of automatically guided vehicles, which has spawned numerous studies and approaches. Research has proceeded as far as a working prototype of a test track with suitable vehicles for an "automated highway". Typically such vehicles have onboard the following:
1) longitudinal control means for acceleration, speed maintenance, and braking, PA0 2) lateral control means for steering, and PA0 3) communications sensor and logic means for receiving collision-avoidance information from onboard or remote sensors, e.g., radar; positioning information from a remote source, e.g., a wire conductor buried in the roadway as a guide; and operating information from a remote computer or remote human operator, e.g., radiocontrol.
The information received and interpreted by the communications sensor and logic means is operatively connected to the lateral and longitudinal control means so that the vehicle safely and effectively moves along the roadway. In other words, the car goes, stops and steers in response to the data received. Numerous articles have been published on such automated highway systems and many patents have been issued on its variations.
Despite the promise of the automated highway and the urgency of its need, the U.S. Department of Transportation stopped funding of automated highway demonstration projects in 1980. Despair over its complexity and high cost has eroded the public desire to fund experiments in this area.
In West Germany and Japan currently funded demonstrations are limited to the less ambitious "automated route guidance," where the driver retains operating control over his/her vehicle. Automated route guidance means that a vehicle's operator can request and get guidance from a central computer about the best route to take from point A to point B. The computer knows the roads, the normal daily traffic patterns, and perhaps the real time situation with respect to traffic accidents and construction tie-ups. The human operator can then read and follow the computer's suggested directions which are communicated to a display terminal in the vehicle. By directing a driver to less traveled routes, the automated route guidance system is able to make more complete use of an area's total network of roads and highways. The use of such a system, however, is limited to regions which have several roadways between points A and B. In other words, there can be no redirection of the vehicle if there is only one roadway.
Another variation of this operator-controlled traffic mitigation system is an automated control system for traffic lights, currently in use in Los Angeles. Under the Los Angeles system, a central computer automatically controls intersection lights in response to actual traffic patterns. This system has had success in relieving traffic congestion during the Olympics. The advantage of this system is limited primarily to preventing gridlock, a traffic condition experienced daily in New York City, where traffic from all directions is stopped at an intersection for extremely lengthy periods. (The system is able to prevent gridlock by anticipating the ingress and egress flow rate of vehicles into and out of an intersection. By appropriately controlling lights at that intersection, the computer is able to balance the two flow rates so that no substantial back-up occurs.) The automated traffic light control system, though a practical tool for traffic intersection control, is inapplicable in solving the problem of getting more cars on a road between A and B.
Some experiments at traffic mitigation have been made with totally self-contained robot-guided vehicles, but so far, little promise has been shown. One such vehicle was equipped with a TV camera to "see" ahead a short stretch of road while driving itself slowly down the road. In that case, the robot vehicle tried to drive itself up a roadside tree. Technicians later explained that the sun's angle had caused the tree shadow to be unexpectedly sharp. The programmers have promised that next year's model will know more about shadows. I believe robots are decades away from being acceptable drivers.
Other prior art systems, in obliquely dealing with the problem of traffic mitigation, have suggested methods of automatically maintaining fixed close distances between two cars, thereby increasing the potential carrying capacity of a roadway. For example, Ayotte, U.S. Pat. No. 4,119,166, teaches a dual vehicle operating system whereby a lead vehicle is physically connected to a trailing vehicle by a zeroforce mechanical connecting link and signal wires. Mechanical transducers in the connecting link and pedal transducers in the lead car provide information via signal wires of the lead vehicle's steering, braking, and acceleration to an electronic control in the trailing vehicle that controls the trailing vehicle's throttle, brakes and steering. In this way, the trailing vehicle mimics the lead vehicle.
Such systems, however, suffer from the obvious disadvantage of requiring a physical hookup. The requirement of a hookup destroys most of the system's usefulness in dealing with the problem of traffic mitigation. The extra time and steps required to both prearrange for a car to be hooked up and to physically hook up the mechanical connection presents a nearly insurmountable barrier to the general and popular usage of this prior art system. Like car pools, this type of system will most likely die for lack of interest.
Reid, U.S. Pat. No. 3,011,580, also teaches an automatic vehicle control system which attempts to accomplish a similar result of closely spaced vehicles on a roadway. In contrast to Ayotte, Reid teaches a system where the steering, braking, and acceleration of a trailing vehicle is controlled by a leading vehicle so as to maintain a predetermined separation between the two vehicles without the use of a physical connecting means. Reid accomplishes this purpose by employing a pick up assembly on the trailing vehicle which detects infrared radiation from the two tail lights of the leading vehicle. The two tail lights and the pick up assembly, which is centered at the front of the trailing vehicle, define three points of a triangle. The angle subtended by the line between the two tail lights is directly proportional to the distance between the two vehicles. To maintain a fixed distance between the two vehicles, Reid controls the trailing vehicle to maintain a constant subtended angle.
One major disadvantage of this type of system is its inability to compensate for differing vehicular performance characteristics of the two vehicles. To take an extreme example, such a system may be dangerously inoperable if a semitrailer is trailing a high performance sports car. In that case, if the sports car either accelerates quickly or makes a sharp turn, the semitrailer with its poor acceleration characteristics and poor turning radius may be unable to follow the sports car, and in its attempt to do so, may overturn.
Another major disadvantage of this type of system is its failure to provide methods of use during actual roadway operation. For example, there is no provision for a vehicle operator to spontaneously engage in this type of an automatic vehicle control system while on the road. Consequently, this type of system appears to similarly require drivers to prearrange getting their vehicles together In addition, there is no provision for vehicles in this system to voluntarily disengage, thereby limiting the trailing operator's driving freedom and the widespread usefulness of this system.
An objective of the present invention is to provide a new system for the cooperative driving of two or more vehicles which minimizes the disadvantages of the prior art. In accomplishing this objective, the present invention has several uses and advantages. One use is for traffic mitigation. It is well known that individual driver reaction time is a major factor in determining the number of vehicles per hour that is able to pass a fixed point on a freeway or a traffic-light-controlled intersection. If all vehicles are cooperatively paired up, the number of individual reaction times is halved (the trailing vehicles effectively have no driver to react). Hence, the number of vehicles per hour would increase substantially, thereby permitting existing roadways to carry more traffic. Specifically, it is estimated that a 60% improvement over present traffic density may be achieved with a 2 foot separation.
A second independent use of the invention would be vehicle delivery. Once two vehicles are cooperatively paired, no operator is required in the trail vehicle Hence, the paired vehicles could be driven to a destination by a single operator. This would be economically beneficial for delivery of new or rental cars, or for returning a car from servicing. Clearly delivering two cars with one driver is less expensive than requiring a driver for each car.
One advantage of using the present invention's system would be a full savings for the trail vehicle. The drafting effect, i.e. the reduction of wind resistance caused by the lead vehicle, is well known by racing drivers. If the distance between the vehicles is small and the aerodynamics well thought out, the drafting effect could save 25 percent or more in fuel costs.